This invention relates to an apparatus having a plasma generating mechanism and to a plasma processing method thereof; and, more particularly, the invention relates to a plasma processing apparatus, which is applicable for use in the fine processing of semiconductor devices, such as semiconductor manufacturing equipment and LCD equipment, and to a working method thereof.
Recent semiconductor processing technologies have been required to have finer processing performance and higher production accuracy. Further, the conventional plasma apparatus, which decomposes process gases by use of a plasma and physically processes semiconductor wafers, cannot be free from the deposition of reaction products on the inner wall of the plasma chamber of the apparatus. This inevitable deposition of a reaction product tends to substantially affect the processing status of wafers. As wafer processing technology advances, this influence becomes greater and the resulting patterns on the semiconductor devices tend to vary, even through the input conditions of the apparatus are kept identical. In other words, this makes the production unstable.
To solve this problem, conventional methods have employed cleaning of the inner walls of the chamber by plasma or controlling of the temperature of the chamber walls so that the reaction products will not deposit thereon. However, most of these methods are not sufficient to keep the wafer processing status identical, so that the wafer processing status keeps on varying gradually as the processing advances from wafer to wafer. Before the products are seriously affected, the plasma processing apparatus must be disassembled for parts replacement and wet cleaning, sometimes using ultrasonic waves. Besides the depositions on the chamber walls, the wafer processing status is also affected by various factors of the processing system, such as temperature. Therefore, various ideas have been employed to eliminate such influences. For example, detecting transitions in the processing status of the plasma processing apparatus and cleaning the chamber according to the result of detection, and feeding back the result of detection to the plasma processing apparatus to keep the processing status constant, have been proposed.
A method of monitoring transitions in processing status of the plasma processing apparatus is disclosed for example by Japanese Patent Publication No. 10-125660 (1998). This method of estimating the performance of an apparatus or diagnosing the plasma status uses a relational expression between plasma processing characteristics and the electric signals of the apparatus. More particularly, the method contains a step of determining an approximate equation expressing the relationship between three electric signals and the plasma processing characteristics of the apparatus in a major regression analysis manner.
Another method is disclosed in Japanese Patent Publication No. 11-87323 (1999). This method employs an existing detecting system comprising a plurality of sensors in the plasma processing apparatus and monitors the device status according to the relationship of the signals from the sensors. Further, this example employs an expression using ratios of six electric signals as a method of creating a relational signal.
Another method is disclosed in U.S. Pat. No. 5,658,423. This method involves taking a lot of signals from a light and mass spectrometer, creating a relational signal thereof, and monitoring the device status with the relational signal. This involves the use of a principal component analysis method as a method to create this relational signal.
However, the method disclosed by Japanese Patent Publication No. 10-125660 (1998) has hardly been put in actual use because the method determines an approximate equation expressing the relationship between three electric signals and plasma processing characteristics of the apparatus on a map which varies input values of part of many processing conditions and requires a measurement of processing characteristics using many wafers. Further, if a plasma input value which is not taken into consideration in the measurement changes, the estimated model expression cannot be used. Furthermore, this method must measure processing characteristics of an enormous number of wafers to reflect a processing characteristic which is difficult to measure and is dependent upon internal conditions (such as the thickness of deposition films which continuously increase as the wafer processing continues) upon the model expression. This makes the method more difficult to be put in practical use.
Additionally, the method disclosed in Japanese Patent Publication No. 11-87323 (1999) is a general method which uses a technique of relating a plurality of well-known detecting means to a plurality of detection signals for diagnosis. Further, the disclosed method of calculating the ratios of some signals for relationship is one of the conventional methods, and it is very difficult to apply the method to a plasma processing system which has various process states dependent upon various factors which are subject to fluctuation.
Unlike this, the method in U.S. Pat. No. 5,658,423 discloses a method of analyzing main components of a lot of data obtained from devices, obtaining device status changes, and thus monitoring plasma states. However, this method still has more items to be improved before being applied to actual plasma processing systems, which must process wafers having various device structures under various conditions.
Accordingly, it is an object of the present invention to provide a method of monitoring a plasma processing apparatus, whose status varies depending upon processing conditions and upon a total number of processed wafers. Further, in this monitoring method, a few items of useful information are extracted from a lot of detection signals automatically, to provide an easy-to-use process monitoring method. A plasma processing apparatus using such a monitoring method and a method of producing devices, such as semiconductor devices and LCD devices, are provided.
In order to attain the above object, a characteristic of the present invention is to provide a plasma processing apparatus having a process chamber to process specimens, comprising: a status detecting unit which detects the processing status of the inside of the process chamber and outputs a plurality of signals, and a signal converting unit which extracts an arbitrary number of signal processing filters from a signal filter database by a signal filter selector means and creates as many device status signals as the filter selected; wherein the signal converting unit creates device status signals having a time series which are less than the output signals.
Another characteristic of the present invention is to provide a mechanism which inputs device status signals and controls devices therewith.
A further characteristic of the present invention is to display the status change of the device signals in accordance with time on a display unit.
A further characteristic of the present invention is to provide means for dividing plasma light by wavelengths as the status detecting unit.
Still another characteristic of the present invention is to provide means for detecting electrical states of arbitrary points in the plasma processing apparatus including plasma as the status detecting unit.
A further characteristic of the present invention is to provide means for dividing electrical status signals by frequencies.
Yet another characteristic of the present invention is to cause the status detecting unit to detect reflected power components when the plasma processing apparatus has a unit for supplying power to the process chamber as plasma generating means.
A more particular characteristic of the present invention is to provide means for adding optical signals to plasma; wherein the status detecting unit detects signals which change while the optical signals pass through the plasma or when the optical signals are reflected by the plasma.
Still another characteristic of the present invention is to provide means for adding electrical signals to the plasma; wherein the status detecting unit detects signals which change while the electrical signals pass through the plasma or when the electrical signals are reflected by the plasma.
A further characteristic of the present invention is to use eigen vectors obtained by principal component analysis of the result of specimen processing the signal filters.
Yet another characteristic of the present invention is to combine eigen vectors obtained by the principal component analysis of the result of specimen processing into a vector and to use the same as the signal filters.
A more particular characteristic of the present invention is to update the database using the result obtained in the processing of some specimens.
Still another characteristic of the present invention is to update the database using data obtained by processing particular specimens (called dummy wafers) in a preset process sequence.
A further characteristic of the present invention is to provide a mechanism to monitor how the database is updated in the plasma processing apparatus.
A further characteristic of the present invention is to stop the use of a certain status detecting means, or to remove the certain status detecting means from the plasma processing apparatus, after the database is created.
Yet another characteristic of the present invention is to obtain or update the database by use of external communication.
A more particular characteristic of the present invention is to provide means for selecting one or more signal filters according to tags, such as numbers or names assigned to the signal filters, wherein the selected signal filters are used to display, output, and control the device status signals of the signal converting unit.
Still another characteristic of the present invention is to provide a list of pre-named device conditions and a mechanism for selecting one named device condition from the device condition list using the device status signals and displaying and outputting named device conditions.
A further characteristic of the present invention is to provide a plasma processing apparatus, wherein the number of device status signals to be output or displayed varies according to the status of devices on the specimens.
A further characteristic of the present invention is to provide a plasma processing apparatus, wherein the number of device status signals to be output varies in response to external requests (from outside the plasma processing apparatus).
Yet another characteristic of the present invention is to provide a judging mechanism which checks whether each device status signal is in a preset range and changes the operating status of the plasma processing apparatus (e.g. cleaning the apparatus, replacement of parts, or start of wafer processing) according to the result of judgment.
A more particular characteristic of the present invention is to provide means for selecting types of specimens to be processed, among specimens requiring a different level of processing accuracy in a single plasma processing apparatus.